[resolved] Customizing Author Pages (2 posts)

I use a two columns theme, with flexible width, and I'm trying now to customize my author pages. I'd like to get them with a width of 100%. So I first removed the sidebar call (in the Page Template), but now I don't know which code I should add (and where) to overpass the posts template (only regarding the width).
I do my best but... I don't know very much about code actually !
Could someone help?
Many thanks, in advance.